Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$234.43	5.328%	$246.9204	$246.92	$246.90	$246.90
Purchase #2	$30.38	11.512%	$33.8773	$33.88	$33.90	$33.90
Purchase #3	$233.90	3.429%	$241.9204	$241.92	$241.90	$241.90
Purchase #4	$212.25	6.133%	$225.2673	$225.27	$225.25	$225.30
Purchase #5	$140.94	7.390%	$151.3555	$151.36	$151.35	$151.40
Purchase #6	$18.63	8.132%	$20.145	$20.15	$20.15	$20.10
Purchase #7	$134.32	11.789%	$150.155	$150.16	$150.15	$150.20
7 purchase totals =	$1,004.85		$1,069.6409	$1,069.66	$1,069.60	$1,069.70